1. Field of the Invention
The invention relates to polyadducts produced from nonlinear-optically active copolymers and polymerizable nonlinear-optically active monomers, i.e., for electrooptical and photonic components.
Electrooptical and photonic components are important elements in nonlinear optics and in optical information technology. They are planar waveguide structures whose function can be altered by an electrical voltage. They comprise modulators, Mach-Zehnder modulators, tunable and switchable directional couplers, wavelength filters, including tunable wavelength filters, and polarization-modifying waveguide components. Their construction is described, for example, by R. C. Alferness in T. Tamir xe2x80x9cGuided-Wave Optoelectronicsxe2x80x9d, Springer-Verlag Berlin, Heidelberg 1988, pages 145 to 210, and in K. J. Ebeling xe2x80x9cIntegrierte Optoelektronikxe2x80x9d, 1st edition, Springer-Verlag Berlin, Heidelberg 1989, pages 152 to 162.
Components of this kind can be produced using highly anisotropic inorganic crystals which have a high 2nd-order susceptibility.
In the past, organic materials and polymers having high 2nd-order susceptibilities have also been developed. They feature considerable advantages in terms of their preparation and their use in electrooptical and photonic components. Polymers having nonlinear-optical (NLO) properties are known from the literature; in this context see, for example: S. R. Marder, J. E. Sohn, G. D. Stucky xe2x80x9cMaterials for Nonlinear Opticsxe2x80x9d, ACS Symposium Series, Vol. 455 (1991), pages 128 to 156, R. A. Norwood et al. in L. A. Hornak xe2x80x9cPolymers for Lightwave and Integrated Opticsxe2x80x9d, Marcel Dekker, Inc., New York 1992, pages 287 to 320, and G. J. Ashwell, D. Bloor xe2x80x9cOrganic Materials for Nonlinear Opticsxe2x80x9d, Royal Society of Chemistry, Cambridge 1993, pages 139 to 155 and 332 to 343.
An overview of current problems in the development of materials having pronounced NLO properties was recently published by T. J. Marks and M. A. Ratner in Angew. Chem. 107 (1995), pages 167 to 187. In addition to the requirements that have to be set for nonlinear-optical chromophores, reference is also made to the problems in developing polymeric matrices for the embedding or binding of chromophores, and their orientation-stable alignment.
In order for such polymers, which are provided with covalently bonded or dissolved NLO chromophores, become nonlinear-optically active and have a high 2nd-order susceptibility, the chromophores must be oriented in an electrical field (in this respect, see: J. D. Swalen et al. in J. Messier, F. Kajzar, P. Prasad xe2x80x9cOrganic Molecules for Nonlinear Optics and Photonicsxe2x80x9d, Kluwer Academic Publishers 1991, pages 433 to 445). This normally takes place in the region of the glass transition temperature, where the mobility of the chain segments of the polymers allows orientation of the NLO chromophores. The orientation obtained in the field is then frozen in by cooling. The 2nd-order susceptibility "khgr"(2) that is achievable here is proportional to the spatial density of the hyperpolarizability xcex2, to the ground-state dipole moment xcexco of the chromophores, to the electrical poling field, and to parameters which describe the distribution of orientation following the poling process (in this respect, see: K. D. Singer et al. in P. N. Prasad, D. R. Ulrich xe2x80x9cNonlinear Optical and Electroactive Polymersxe2x80x9d, Plenum Press, New York 1988, pages 189 to 204).
Great interest attaches to compounds combining high dipole moment with high values of xcex2. Consequently, investigation has focused in particular on those chromophores which consist of conjugated xcfx80 electron systems that carry an electron donor at one end and an electron acceptor at the other end and are covalently bonded to a polymer: for example, to polymethyl methacrylate (U.S. Pat. No. 4,915,491), polyurethane (EP-A 0 350 112), or polysiloxane (U.S. Pat. No. 4,796,976).
One particular problem of said polymer materials having NLO properties is the relaxation of the oriented chromophore units and thus the loss of NLO activity. At present, this relaxation is still preventing the production of electrooptical components with long-term stability that are deployable technically.
It is therefore the object of the present invention to provide nonlinear-optically active copolymers and polyadducts produced from them by means of which post-orientation relaxation of the nonlinear-optically active units in the NLO polymers is prevented or at least retarded. Moreover, the nonlinear-optically active polymers should exhibit low optical losses. The aim of the present invention is in particular to provide NLO polymers with which relaxation of the chromophores is prevented up to temperatures of above 100xc2x0 C. and which comprise those nonlinear-optical units which ensure thermal stability at temperatures of more than 200xc2x0 C. In addition to this, the NLO polymers should allow extremely wide variation of the optical properties of the electrooptical and photonic components.
In order to achieve this object the present invention provides nonlinear-optically active copolymers of the general formula 1 
in which R1, R2, R3, X1, X2, X3, Y1, Y2, Y3, Z, l, m and n are as defined below. These are, therefore, nonlinear-optical, glycidyl-functional copolymers which in accordance with the invention can be reacted by crosslinking with a carboxyl-functional polyester having an appropriate degree of polymerization, to give the polyadducts that are likewise of the present invention.
The use of polyadducts based on glycidyl-functional nonlinear-optically active copolymers is known per se. DE-A 196 39 381 proposes a material for which a polymer comprising a nonlinear-optical group and glycidyl groups is crosslinked by coreaction with cyanates or prepolymers in order to achieve a stable orientation of the chromophore units. However, it has been found that the resulting material possesses only a low film-forming tendency, and low thermal stability under poling conditions.
Surprisingly, it has been possible to eliminate these is disadvantages by virtue of the nonlinear-optically active copolymers of the general formula 1 of the present invention and, respectively, by the polyadducts obtained from them by crosslinking with a carboxyl-functional polyester.
The nonlinear-optical polyadducts of the present invention are prepared by crosslinking a nonlinear-optically active copolymer of the general formula 1 having a proportion from 5 to 95 mol % of glycidyl groups, preferably from 20 to 80 mol %, and having a proportion of from 5 to 95 mol %, preferably from 20 to 80 mol %, of simple linear or branched and also cyclic esters, preferably of the cyclohexyl series, with at least one carboxyl-functional polyester. Advantageously, there are from 0.1 to 5 gram equivalents of the polyester component, based on the number of carboxyl groups employed, preferably from 0.4 to 2.7 gram equivalents, per gram equivalent of glycidyl groups of the NLO copolymer. As a result of the coreaction of the glycidyl groups of the NLO copolymer and the polyester component, tightly crosslinked polymer layers are produced in the polymer film.
In the production of the electrooptical or photonic components, the above-mentioned orientation and crosslinking take place on a support, where the crosslinked polyadduct forms the functional layer which is arranged between two buffer layers. With advantage, one or both buffer layers of the electrooptical or photonic components according to the invention can also consist, like the functional layer, of an appropriate crosslinked NLO polymer. It is known that in that case the refractive index of the buffer layers is somewhat lower than that of the functional layer. The required difference in refractive index (from the light-guiding functional layer or from its waveguide structure) is established by means of an appropriate composition of the copolymers with and without nonlinear-optical units.
The nonlinear-optically active, glycidyl-functional copolymers are preferably compounds of the general formula 1:
In this formula:
R1, R2, R3 are identical or different from one another and are H, CH3 or halogen;
X1, X2, X3 are identical or different from one another and are O or NR4, where R4 is H or a linear or branched C1- to C6- -alkyl radical;
Y1 is a linear or branched hydrocarbon chain having 2 to 20 carbon atoms, where one or more nonadjacent CH2 groups, with the exception of the CH2 group providing the link to the radical Z, can be replaced by O, S or NR5, where R5 is H or a linear or branched C1- to C6- alkyl radical;
Y2 is a linear or branched hydrocarbon chain having 1 to 3 carbon atoms;
Y3 is a linear or branched C1- to C20- alkyl radical, a C5-  to C7- cycloalkyl radical or a bi- or tricyclic alkyl radical having up to 18 carbon atoms;
Z is a nonlinear-optically active group; and
l:m:n=1 . . . 99:1 . . . 99:1 . . . 99.
Preferably, in the copolymer of formula 1:
R1=R2=R3=CH3,
X1=X2=X3=O,
Y1=(CH2)o, where o=2 to 6,
Y2=CH2,
Y3=cyclohexyl, norbornyl, adamantyl or methyl, and
l:m:n=10 . . . 50:10 . . . 30:20 . . . 80.
The radicals R4 and R5, which can be the same or different, are in particular a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, pentyl, isopentyl, neopentyl, hexyl or 2-methylpentyl radical.
The nonlinear-optically active group Z can, for example, be a chromophore of the azo dye, stilbene dye, or polymethine dye type. Preferably, the group Z has a structure of the general formula 2: 
which is attached by D to Y1 and where
D is O, S or NR9 where R9 is a hydrogen atom, a linear or branched C1- to C20- alkyl radical which is uninterrupted or interrupted by 1 to 5 oxygen atoms in ether function, or is a benzyl radical or a phenyl or naphthyl radical, or R9 and Y1 together with the nitrogen atom connecting them, form a pyrrolidinyl, piperidinyl, morpholinyl or piperazinyl radical,
R6, R7, R8 are independently of one another a hydrogen atom, a linear or branched C1- to C20- alkyl radical which is uninterrupted or interrupted by 1 to 5 oxygen atoms in ether function or are a phenyl, naphthyl, thienyl, thiazolyl or pyridyl radical,
Q is an electron-acceptor-substituted methylene or imino group,
A is S, O. NR10 or a ring double bond, or is 
where R10 is a hydrogen atom, a linear or branched C1- to C20- alkyl radical or a phenyl or naphthyl radical and T is CH or N or, if desired, Q and T together form a structure of the type xe2x95x90Nxe2x80x94SO2xe2x80x94Cxe2x89xa1, xe2x95x90Nxe2x80x94CSxe2x80x94Cxe2x89xa1 or xe2x95x90Nxe2x80x94COxe2x80x94Cxe2x89xa1, and
B is a CH or CR11 group or is N, where R11 is a linear or branched C1- to C20- alkyl radical, a phenyl radical or a naphthyl radical.
The radicals R6 to R11 can in particular be a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, 2-methyl-pentyl, heptyl, octyl, 2-ethylhexyl, isooctyl, isononyl, decyl or isodecyl radical, and also the corresponding alkoxy or alkenyl radicals (the terms isooctyl, isononyl and isodecyl in this list are trivial names derived from the alcohols obtained in an oxo synthesis; in this respect, see: xe2x80x9cUllmann""s Encyclopedia of Industrial Chemistryxe2x80x9d, 5th Edition, Vol. A1, pages 290 to 293, and Vol. A10, pages 284 and 285).
With particular preference, R6, R7 and R8 are each a nitrogen atom, A is a sulfur atom or a 1,2-fused benzene ring, B is a CH group, and Q is a dicyanomethylene group. Furthermore, Q and T together preferably form a structure xe2x95x90Nxe2x80x94SO2xe2x80x94Cxe2x89xa1. Q can, moreover, be an alkoxycarbonylcyanomethylene, cyanoimino or alkoxycarbonylimino group. D is preferably a substituted amino radical.
Compounds of the general formula 2 are described in detail in the simultaneously filed German Patent Application 198 10 030.2 (xe2x80x9cChromophoric compounds and process for their preparationxe2x80x9d).
Z can also be an azamethine of the following structure 2B: 
which is linked to Y1 through R12 and where
R12 and R13 are identical or different from one another and are in each case a linear or branched C1- to C20- alkyl radical which can be interrupted by up to five ether oxygen atoms, a phenyl, naphthyl, thienyl, thiazolyl or pyridyl radical or R12 and R13 together form a five- or six-membered carbocyclic or heterocyclic ring;
R14 is a hydrogen atom, a hydroxyl or acyloxy group, a linear or branched C1- to C20- alkyl radical or a phenyl radical which is optionally substituted in the para position by a halogen, hydroxyl or acyloxy group;
G denotes S, Se, O or NR4, where R4 is a hydrogen atom or a linear or branched C1- to C20- alkyl radical, or denotes a ring double bond or a 1,2-fused benzene ring;
E denotes a CH or CR5 group, where R5 is a linear or branched C1- to C20- alkyl radical, a phenyl or a naphthyl radical, or denotes N; and
M denotes S, Se, O or NR6, where R6 is a hydrogen atom or a linear or branched C1- to C20- alkyl radical, or denotes a ring double bond or a 1,2-fused benzene ring;
T and L are identical or different from one another and each denotes a CH or CR7 group, where R7 is a C1- to C20- alkyl radical, an optionally substituted phenyl or a naphthyl radical, or denotes N, or T and L together denote a ring double bond or a 1,2-fused benzene ring, with the proviso that when G is a ring double bond, T and L together and M are not simultaneously a ring double bond and a 1,2-fused benzene ring; and
Acc is a nitrile, C1- to C20- alkoxycarbonyl, formyl, acyl, arylsulfonyl or nitro group.
Compounds of this kind are described in detail in the simultaneously filed German Patent Application 198 10 063.9 (xe2x80x9cProcess for preparing azamethines, and azamethines themselvesxe2x80x9d).
The nonlinear-optically active copolymers are amorphous copolymers comprising comonomers which have covalently bonded nonlinear-optical molecule units and comonomers with crosslinking-active functional groups. The preparation of the copolymers by free-radical polymerization and the synthesis of the precursors take place either in accordance with the conventional processes and/or are described in the working examples.
The free-radical polymerization is able to take place by means of free-radical initiators which decompose on heating. Initiators of this kind which are used are preferably azoisobutyronitrile and peroxy compounds, such as dibenzoyl peroxide.
The role of crosslinking-active component in the present invention is played by a carboxyl-functional polyester of the general formula 3: 
In this formula, p denotes values between 10 and 350, preferably between 100 and 150. These values represent degrees of polymerization which are suitable in the context of the present invention. The polyesters are either commercially available or can be produced by corresponding polymerization of a suitably substituted isophthalic acid ester.
To improve the surface quality, the processability and/or the compatibility with polymers it is possible to add processing auxiliaries to the polyadducts of the invention, depending on the intended application. Examples of these auxiliaries are thixotropic agents, flow-control agents, plasticizers, wetting agents, lubricants, and binders.
The polyadducts according to the invention are applied in dissolved or liquid form, together if desired with crosslinking-active compounds or initiators, to a substrate by spin coating, dipping, printing or brushing. In this way a nonlinear-optical arrangement is obtained in which the polyadducts or corresponding prepolymersxe2x80x94before or during crosslinkingxe2x80x94are given a polar alignment in electrical fields. After cooling, polymer materials having excellent nonlinear-optical properties andxe2x80x94by virtue of the crosslinkingxe2x80x94increased orientation stability and thus increased long-term stability, even at relatively high service temperatures, are obtained.
In order to produce the nonlinear-optical materials it is particularly advantageous to use oligomeric prepolymers of the adducts of the invention. These prepolymers are prepared conventionally, with the copolymers comprising nonlinear-optically active glycidyl groups and simple linear, branched or cyclic esters being reacted with an excess of the carboxyl-functional polyester compound. Following application to a substrate, the prepolymers undergo polar alignmentxe2x80x94at a temperature above the glass transition temperaturexe2x80x94and are subsequently crosslinked in an applied electrical field to give the nonlinear-optical polyadducts having an improved profile of properties.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in nonlinear-optically active copolymers, polyadducts produced from them, and their use for nonlinear-optical media, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments.